1. Technical Field
The present invention relates to a light guide plate used for a head-mount display or the like used while worn on the head, and a virtual image display device incorporating the light guide plate.
2. Related Art
In recent years, as a virtual image display device such as a head-mount display for making formation and observation of a virtual image possible, there have been proposed various devices of a type of guiding the picture light from the display element to the pupils of the observer using a light guide plate. As such a light guide plate for a virtual image display device, there has been known a light guide plate, which guides the picture light using total reflection, reflects the picture light with a plurality of partial reflecting surfaces disposed in parallel to each other at a predetermined angle with a principal surface of the light guide plate, and thus outputs the picture light to thereby make the picture light reach the retinas of the observer (see JP-T-2003-536102 (the term “JP-T” as used herein means a published Japanese translation of a PCT patent application) and JP-A-2004-157520). The plurality of partial reflecting surfaces provided to the light guide plate can be made as what is obtained by providing a reflecting layer to the part having, for example, a sawtooth cross-sectional shape (see, e.g., JP-A-2004-157520, FIG. 5).
In the case of taking out the light beam from the light guide plate provided with the plurality of partial reflecting surfaces parallel to each other as described above, since there occurs the difference in the width of the light beam which can be taken therefrom between the partial reflecting surfaces disposed along the light guide direction of the light guide plate due to the difference in the total reflection angle inside the light guide plate between the light beams, there is a possibility that the resolution of the image is degraded locally.